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Lowering springs for oem boss shocks

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good day,

i am planing to lower my car and at the same time i would like the best springs for track racing my boss 302.

My boss has full front stock suspension ( other than blowfish brake cooling ducts) and rear stock suspension with bmr ucas, lcas and relocation brackets.

I think i would need panhard bar to re align the diff after lowering the car... do i also need more parts to change too ?

There are many spring heights and rates and if other mods are required other than the panhard bard please advise.
 

Norm Peterson

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When you say 'track', do you mean mostly road courses or mostly drag strips and other forms of straight line running?

My personal thoughts as far as choosing springs goes is to choose based on spring rates for your use and generally shoot for less lowering rather than more. Function > appearance if you're not being judged at a car show.


Norm
 
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When you say 'track', do you mean mostly road courses or mostly drag strips and other forms of straight line running?

My personal thoughts as far as choosing springs goes is to choose based on spring rates for your use and generally shoot for less lowering rather than more. Function > appearance if you're not being judged at a car show.


Norm
Thank you for your input.

I drive my car in circuit track. And yeah with regards to lowering i dont prefer slamming the car to the ground and i am all about function for racing im not into looks and car shows.
 
Many people have had success with the Ford Racing P springs. They do make a boss specific T spring which should work well also. If you want more of a hardcore spring then the H&R race springs or Maximum Motorsport springs would be a good bet. I would recommend an adjustable panhard bar not only to center the axle but it makes the car more predictable not having the deflection of the original bushing.
 
I have the T springs on my 13 boss with stock suspension, everything seems to work well together. It does take nearly all of the rake out of the car though if that's a concern for you.
 
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The Boss 302, especially the Boss302 LS version is a serious road car, if you don't find what you are looking for, I'd research those parts and go that route.
 

Dave_W

Cones - not just for ice cream
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Steeda also has a Boss-specific set of lowering springs. They also sell the Ford Racing "P" spring set for Bosses.
 
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Thabk you guys but these are so many options to choose .... is their spraing rates close to each other ? Is there one better than other for track racing ??

I think the lower the car the better it is at the track or is that not true ?? Because in case if it isnt i think ill go for the p springs from ford performance.
 
If your looking for pure track performance and want to stick to OEM style springs and not coilovers. H&R race springs or MM springs are your best bet, I think they have the highest rate of any stock type spring and I think they are the same spring so whichever you can get cheaper. Mind you they don't ride very nice on the road but they are tolerable.
 

Dave_W

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I think the lower the car the better it is at the track or is that not true ??

Only if the suspension geometry is changed to compensate. In theory, when designing a car the lower the Center of Gravity the better, but in practice on a car that's already built, lowering the car changes the angles of the suspension arms and steering tie rods from their designed range. Lowering "too much" can change the angles to the point that handling becomes worse than stock due to increases in roll center migration and bump steer. That's why both the Ford "P" and Steeda springs only lower the front end a small amount. (I don't know about the other springs mentioned.) They lower the rear a bit more as the rear axle roll center geometry is less sensitive to lowering because of the panhard bar design. For changes in anti-squat from lowering, the easy fix is a set of rear lower control arm relocation brackets. An adjustable panhard bar can re-center the axle if you lower a good amount in the rear and want to get fancy. Lowering the rear a lot can change differential pinion angle, necessitating adjustable rear lower and/or upper control arms. As you can see, the more you lower the car, the more other things need to be changed to compensate.
 

Norm Peterson

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I think the lower the car the better it is at the track or is that not true ?? Because in case if it isnt i think ill go for the p springs from ford performance.
In addition to what Dave_W just posted, lowering a strut-suspended car generally does not gain as much cornering performance as the visual amount of lowering may suggest. While it's true that the total amount of lateral load transfer is reduced, more of that load transfer is being taken through the suspension and the amount of roll would increase if you held the spring stiffnesses the same as before. That's because the geometric roll center drops quite a bit more than the amount you lower the car (double being a reasonable estimate without making all the necessary measurements). In normal situations, at least some of the extra stiffness you paid to get along with the lowering is more or less "wasted" just keeping the car from rolling any more than it did when it was 100% stock. Wheel camber, and tire grip being a vague function of camber are the downstream effects.

Yes, lowering the CG height reduces the total load transfer, so the outboard tires effectively do "gain" in terms of friction coefficient. However, the inboard tires stay loaded a bit more than before, so their effective "mu" value drops a little. Overall, the net gain is less than the gain looking at the outboard tires alone. Lowering a car with a 20" CG height by 2" (10%) might buy you a 3% skidpad improvement in the 1.0 - 1.1g cornering neighborhood. Of course you'd chase 3% effects if you were actually competing (and driving consistently enough to be able to reliably take advantage of it). For a dual-purpose street/HPDE track car, perhaps not. Particularly not if, as Dave has mentioned, you don't include corrections for things like anti-squat/axle roll steer and bumpsteer in your build that your lowering would have affected.

I think people tend to overlook what a stock/stockish ride height Mustang is capable of, and see "more" only as being "more than not very good".


Stock height (and soft stock springs). Aim Solo datalogging. Mild suspension mods (sta-bars, shocks/struts, and alignment, nothing crazy or secretive going on here) and a better wheel (18x11) & tire (MPSS) package than stock, but the OE ride height and spring stiffnesses aren't limiting it all that badly.
1.30g.jpg

15-2-4 T'bolt T12.jpg


Norm
 
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An outstanding example of what Dave is talking about is the old SN95 platform with it's "triangulated 4 link" design. the car had monster wheel gap so everyone bought lowering springs. Problem is, that design uses the trailing arms to locate the diff side to side, lowering the car puts those upper arms in a bind, creating a huge snap oversteer condition on corner exit.
 

Norm Peterson

Corner Barstool Sitter
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a few miles east of Philly
That's why both the Ford "P" and Steeda springs only lower the front end a small amount. (I don't know about the other springs mentioned.)
I can fill in a little information here.

If you put BMR's GT500 handling springs on a "regular" GT, you end up with significantly less lowering than the 1.5" claimed for the heavier GT500. Like only about 0.5" up front and a little over 1" out back. It's not all that difficult to shim out some or all of the inch of rear lowering.

You also gain 20 lb/in of spring rate over the non-GT500 handling springs.

Norm
 

Norm Peterson

Corner Barstool Sitter
939
711
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
An outstanding example of what Dave is talking about is the old SN95 platform with it's "triangulated 4 link" design. the car had monster wheel gap so everyone bought lowering springs. Problem is, that design uses the trailing arms to locate the diff side to side, lowering the car puts those upper arms in a bind, creating a huge snap oversteer condition on corner exit.
I doubt very many people who lowered a Fox/SN95 Mustang or a RWD GM Intermediate (same basic triangulated 4-link geometry) ever realized that as they lowered the rear of their cars, the rear roll center moved UP rather than down like you might expect.

What's even scarier is that there were people who would use polyurethane in the uppers, or add a Panhard bar. Like there wasn't enough bind in the OE configuration so they had to add even more . . .


Norm
 

Grant 302

basic and well known psychic
That's why both the Ford "P" and Steeda springs only lower the front end a small amount.
I liked this post, aside from this part. Even the P springs affect the front geometry quite a bit. Enough so, that I would recommend tall ball joints (and the required bumpsteer kit) to ‘fix’ or compensate for the changes even at that level. Even with coilovers, my front end is ~7/16” higher than P springs that I used before the swap.

And for the rear...most brackets tend to ‘overcorrect’ a 1” drop with (typically) a minimum of a 2” adjustment.

If you put BMR's GT500 handling springs on a "regular" GT, you end up with significantly less lowering than the 1.5" claimed for the heavier GT500. Like only about 0.5" up front and a little over 1" out back. It's not all that difficult to shim out some or all of the inch of rear lowering.

You also gain 20 lb/in of spring rate over the non-GT500 handling springs.

Norm (and I) are not the norm regarding ride height and front geometry. ;)

🤔

...Although I am not the norm for so many other reasons. 😁
 

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